I haven't personally used them, but dpcloud looks like it might do what you want. You could also look into the possibility of using a livecasting service like Vokle/uStream/Justin.tv/LiveStream with a screen-recording tool. (Both approaches would just transmit a live recording of you navigating the presentation yourself. Vokle also has a system for taking audience questions.)
Another option would be to use Simple HTML Slides. It's not a hosted offering, but all it needs for running the sync server is the smallest, cheapest web host you can find that offers PHP and Memcached (eg. a few-dollar VPS, your own PC with a DynDNS Free account to hook up a domain name, etc.). Synchronized remote presentations is the whole reason it was written.
It also has instructions for converting from PDF (though, if you don't have iPhoto, you'll need to look up another way to go from PDF to a set of JPEG/PNG images) and the author recently took a blog post about what a web-based Powerpoint/Keynote killer must do and converted it into a scorecard/checklist for Simple HTML Slides.